There was a lot more than that..
For starters the aliens left behind all of their injured people. Thats how the alien got there. Gibson chopped his fingers off earlier in the movie, thus leaving him behind. There is a bigger story than just the wife saying "Swing away Meril" The boy had asthma so the alien's poisonous gas did not get into his lungs. The little girl happend to leave water everywhere (which ultimately killed the alien). I liked M. Night's creativity near the end, when you see the alien through the TV you are definately not expecting it, I thought it was brilliant. I loved that movie, some people just have different tastes in movies.
